The invention concerns a light-firable or activatible thyristor formed of a semiconductor body having an N-emitter layer provided with a first electrode, a P-emitter layer provided with a second electrode, and two base layers therebetween.
Light-firable thyristors are mentioned, for example, in the book by E. Spenke, "pn-Transitions" (Vol. 5 of the Series "Semiconductor Electronics"), Springer Publishing Company, Berlin, 1979, on page 119, incorporated herein by reference. Their firing sensitivity must be accommodated to controlled light sources which have only a small light power. If one increases the firing sensitivity by means of the elimination of fixed emitter short circuits, then one simultaneously decreases the stability of the thyristor, that is, its insensitivity to undesired firing processes.